Combustion by-products such as soot, ash and slag often accumulate on the interior of industrial boilers, for example on the boiler tube surfaces. These accumulations dramatically decrease the efficiency of the heat transfer to the boiler tubes. Sootblowers are commonly used to remove the accumulated soot to increase efficiency.
A sootblower usually has a long, steam-carrying lance mounted on parallel tracks that are in turn mounted to an elongated inverted U-shaped sheet-metal housing on the exterior of the boiler. A gear-driven carriage moves the lance tube forward toward the boiler, injecting it into the interior of the boiler through an injection port in the side of the boiler.
After a nozzle at the forward end of the lance tube is injected into the boiler interior, steam is discharged through the nozzle against the interior surfaces of the boiler, blasting soot, ash and slag off the surfaces. The gear drive and carriage then reverse direction to retract the lance from the boiler. In addition to the horizontal travel of the lance along the tracks, the lance is rotated about its longitudinal axis as it travels into and out of the boiler.
Most industrial sootblowers are used in extremely harsh environmental conditions. The interior temperature of the boiler is typically very high, while the exterior temperature is much lower. The lance tube is therefore exposed to wide variations in temperature as it is injected into and removed from the boiler. Further, some combustion by-products are highly corrosive, and may escape from the boiler through the lance injection ports.
Conventional sootblowers include a pair of parallel tracks mounted to the interior of an inverted U-shaped sheet metal housing to carry a gear-driven carriage that drives the lance tube into and out of the boiler through the lance injection-port. The housing serves as the support structure for the tracks and carriage of the sootblower assembly. In some cases, the housing is designed to completely cover the lance tube throughout its length from the boiler outward. The housing is closed on three sides and therefore acts as a hood; it is open on the underside, but closed on the top and sides.
The sootblower assembly is mounted above ground. In conventional sootblower assemblies, the rearward end of the housing is often supported above the floor with either ceiling hangers or a floor support. The forward end of the housing is attached to the boiler. Conventional sootblowers usually have no intermediate support members between the boiler wall and the rearward end of the assembly.
Due to the weight of the gear-driven carriage and lance tube, the sheet metal housing has a tendency to flare as the lance tube moves within the housing, causing misalignment of the normally parallel tracks.
Additionally, heat tends to accumulate within the hoodlike housing, and it is difficult to dissipate. Similarly, the corrosive combustion by-products escaping from the boiler's combustion chamber through the lance injection port tend to accumulate within the housing.
The combination of heat and corrosive by-products accumulation in the housing, and the difficulty in dissipating either therefrom, often lead to warping and corrosion of the entire sootblower. Warping leads to misalignment of the tracks, causing excessive wear on the drive system and even failure of the carriage and gear drive assembly. Corrosion weakens the sootblower components, contributing to misalignment problems and failure of steam pipes and the like.
As a result, conventional sootblowers require frequent inspection and maintenance to remove rust, replace leaking pipes, and repair misaligned tracks and worn drive system components. Nevertheless, sootblower inspection and maintenance can be unpleasant and dangerous, and therefore neglected, because of the danger from exposure to heat and corrosive compounds.
Accordingly, there is a need for a sootblower assembly with a frame construction that eliminates the foregoing problems including warping and misalignment problems caused by weight, heat and corrosive conditions, thereby allowing easier and safer maintenance. These are the primary objectives of the present invention.